Here is the problem, I've gone over anything.
Reason 1: Playstyle. Playstyles are hard to nail down, region-to-region and team-to-team, but NA has a specific playstyle. NA is very, very proactive, way more than any region. This causes a huge snowball, if they miss a timing they lose a massive amount of control or they get a pick and gain a ton of momentum in the round. Here's the issue, Brazil/Asia play really bundled and EMEA has extremely tight defaults. NA teams still rely heavily on just poking around to get a 1v1, but against global competition it's rarely ever a 1v1. This is why NA relied and used chamber so much better than the other regions, it allowed the best mechanical player to poke around with multiple safety options. The second part of the NA playstyle is partly becuase of this proactivity. NA Team are great individual players; NA teams are shitty teams. Look at NRG today, they had more success as individuals, but 2 MIBR players can play better off eachother than 3 NRG members. I'm refering more to midround utility, trading, and holding effective positions with the team and less of just running set plays. Look at how many times Ardiis played an angle and died without anything close to a trade. NA teams don't capitalize on their teammates like everyone else does.
Reason 1 TLDR - NA players do very well on their own, but are innately countered by the playstyles of other regions
Reason 2: Our IGL's are shit. Runi is the best fragging IGL, stellar is too inconstant to put up there. Runi is very good, he's super effective in his role while being an IGL. ALL THE GOOD FRAGGING IGL'S ARE IN FUCKING T2. EVEN FUCKING SHAZ WOULD DO BETTER THAN BOOSTIO, DEPH, AND FNS. AT LEAST FNS CALLS BETTER THAN MOST, BUT HE CAN'T FRAG FOR SHIT. JohnQT, previously mentioned Shahz, Valyn, even fucking Zander. All could produce better than those 3 fucks. This isn't a matter of "all our good players are in ascension", it's a matter of underproducing IGL's not being covered for, except for FNS cause he does call better than Boostio and Deph. But other than FNS, can you say any IGL in NA is better than most other franchised IGL's? Not really.
Reason 2 TLDR - NA IGL"s are below average players, and below average compared to other region's IGL's
Other things people say is that NA is spread too wide, I don't really think so (other than the small-time IGL's having better mechanics and maybe that M80 is better than EG). I do think though that the gap is being overstated. C9 still took a map of Loud. NRG and MIBR went to 3 close maps.